The flowering plants, also known as angiosperms, Angiospermae[5][6] or Magnoliophyta,[7] are the most diverse group of land plants, with 416 families, approximately 13,164 known genera and c. 295,383 known species.[8] Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, and the production of fruits that contain the seeds. Etymologically, angiosperm means a plant that produces seeds within an enclosure; in other words, a fruiting plant. The term comes from the Greek words angeion ("case" or "casing") and sperma ("seed").

The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago (mya), and the first flowering plants are known from 160 mya, they diversified extensively during the Lower Cretaceous, became widespread by 120 mya, and replaced conifers as the dominant trees from 100 to 60 mya.

Angiosperms differ from other seed plants in several ways, described in the table below, these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.[a]

Distinctive features of angiosperms

Feature

Description

Flowering organs

Flowers, the reproductive organs of flowering plants, are the most remarkable feature distinguishing them from the other seed plants. Flowers provided angiosperms with the means to have a more species-specific breeding system, and hence a way to evolve more readily into different species without the risk of crossing back with related species. Faster speciation enabled the Angiosperms to adapt to a wider range of ecological niches, this has allowed flowering plants to largely dominate terrestrial ecosystems.[citation needed]

Stamens are much lighter than the corresponding organs of gymnosperms and have contributed to the diversification of angiosperms through time with adaptations to specialized pollination syndromes, such as particular pollinators. Stamens have also become modified through time to prevent self-fertilization, which has permitted further diversification, allowing angiosperms eventually to fill more niches.

The male gametophyte in angiosperms is significantly reduced in size compared to those of gymnosperm seed plants.[9] The smaller size of the pollen reduces the amount of time between pollination — the pollen grain reaching the female plant — and fertilization; in gymnosperms, fertilization can occur up to a year after pollination, whereas in angiosperms, fertilization begins very soon after pollination.[10] The shorter amount of time between pollination and fertilization allows angiosperms to produce seeds earlier after pollination than gymnosperms, providing angiosperms a distinct evolutionary advantage.

Closed carpel enclosing the ovules (carpel or carpels and accessory parts may become the fruit)

The closed carpel of angiosperms also allows adaptations to specialized pollination syndromes and controls. This helps to prevent self-fertilization, thereby maintaining increased diversity. Once the ovary is fertilized, the carpel and some surrounding tissues develop into a fruit, this fruit often serves as an attractant to seed-dispersing animals. The resulting cooperative relationship presents another advantage to angiosperms in the process of dispersal.

Reduced female gametophyte, seven cells with eight nuclei

The reduced female gametophyte, like the reduced male gametophyte, may be an adaptation allowing for more rapid seed set, eventually leading to such flowering plant adaptations as annual herbaceous life-cycles, allowing the flowering plants to fill even more niches.

In general, endosperm formation begins after fertilization and before the first division of the zygote. Endosperm is a highly nutritive tissue that can provide food for the developing embryo, the cotyledons, and sometimes the seedling when it first appears.

The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms, the vascular bundles of the stem are arranged such that the xylem and phloem form concentric rings.

In the dicotyledons, the bundles in the very young stem are arranged in an open ring, separating a central pith from an outer cortex; in each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles (interfascicular cambium), a complete ring is formed, and a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside, the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.

Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue, they contain no cambium and once formed the stem increases in diameter only in exceptional cases.

The characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, and provide the most trustworthy external characteristics for establishing relationships among angiosperm species, the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally on a shoot or from the axil of a leaf (where the petiole attaches to the stem). Occasionally, as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More typically, the flower-bearing portion of the plant is sharply distinguished from the foliage-bearing or vegetative portion, and forms a more or less elaborate branch-system called an inflorescence.

There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens (or microsporophylls). The "female" cells called megaspores, which will divide to become the egg cell (megagametogenesis), are contained in the ovule and enclosed in the carpel (or megasporophyll).

The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Usually, other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators, the individual members of these surrounding structures are known as sepals and petals (or tepals in flowers such as Magnolia where sepals and petals are not distinguishable from each other). The outer series (calyx of sepals) is usually green and leaf-like, and functions to protect the rest of the flower, especially the bud, the inner series (corolla of petals) is, in general, white or brightly colored, and is more delicate in structure. It functions to attract insect or bird pollinators. Attraction is effected by color, scent, and nectar, which may be secreted in some part of the flower, the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans.

While the majority of flowers are perfect or hermaphrodite (having both pollen and ovule producing parts in the same flower structure), flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization. Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot easily transfer pollen to the pistil (receptive part of the carpel). Homomorphic flowers may employ a biochemical (physiological) mechanism called self-incompatibility to discriminate between self and non-self pollen grains; in other species, the male and female parts are morphologically separated, developing on different flowers.

The botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon (bottle, vessel) and σπέρμα, (seed), was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked, the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any approach to its modern scope became possible only after 1827, when Robert Brown established the existence of truly naked ovules in the Cycadeae and Coniferae,[11] and applied to them the name Gymnosperms.[citation needed] From that time onward, as long as these Gymnosperms were, as was usual, reckoned as dicotyledonous flowering plants, the term Angiosperm was used antithetically by botanical writers, with varying scope, as a group-name for other dicotyledonous plants.

An auxanometer, a device for measuring increase or rate of growth in plants

In 1851, Hofmeister discovered the changes occurring in the embryo-sac of flowering plants, and determined the correct relationships of these to the Cryptogamia, this fixed the position of Gymnosperms as a class distinct from Dicotyledons, and the term Angiosperm then gradually came to be accepted as the suitable designation for the whole of the flowering plants other than Gymnosperms, including the classes of Dicotyledons and Monocotyledons. This is the sense in which the term is used today.

In most taxonomies, the flowering plants are treated as a coherent group, the most popular descriptive name has been Angiospermae (Angiosperms), with Anthophyta ("flowering plants") a second choice. These names are not linked to any rank, the Wettstein system and the Engler system use the name Angiospermae, at the assigned rank of subdivision. The Reveal system treated flowering plants as subdivision Magnoliophytina (Frohne & U. Jensen ex Reveal, Phytologia 79: 70 1996), but later split it to Magnoliopsida, Liliopsida, and Rosopsida, the Takhtajan system and Cronquist system treat this group at the rank of division, leading to the name Magnoliophyta (from the family name Magnoliaceae). The Dahlgren system and Thorne system (1992) treat this group at the rank of class, leading to the name Magnoliopsida, the APG system of 1998, and the later 2003[12] and 2009[13] revisions, treat the flowering plants as a clade called angiosperms without a formal botanical name. However, a formal classification was published alongside the 2009 revision in which the flowering plants form the Subclass Magnoliidae.[14]

The internal classification of this group has undergone considerable revision, the Cronquist system, proposed by Arthur Cronquist in 1968 and published in its full form in 1981, is still widely used but is no longer believed to accurately reflect phylogeny. A consensus about how the flowering plants should be arranged has recently begun to emerge through the work of the Angiosperm Phylogeny Group (APG), which published an influential reclassification of the angiosperms in 1998. Updates incorporating more recent research were published as the APG II system in 2003,[12] the APG III system in 2009,[13][15] and the APG IV system in 2016.

which in the Cronquist system are called Magnoliopsida (at the rank of class, formed from the family name Magnoliaceae) and Liliopsida (at the rank of class, formed from the family name Liliaceae). Other descriptive names allowed by Article 16 of the ICBN include Dicotyledones or Dicotyledoneae, and Monocotyledones or Monocotyledoneae, which have a long history of use. In English a member of either group may be called a dicotyledon (plural dicotyledons) and monocotyledon (plural monocotyledons), or abbreviated, as dicot (plural dicots) and monocot (plural monocots), these names derive from the observation that the dicots most often have two cotyledons, or embryonic leaves, within each seed. The monocots usually have only one, but the rule is not absolute either way, from a broad diagnostic point of view, the number of cotyledons is neither a particularly handy nor a reliable character.

The exact relationship between these eight groups is not yet clear, although there is agreement that the first three groups to diverge from the ancestral angiosperm were Amborellales, Nymphaeales, and Austrobaileyales.[17] The term basal angiosperms refers to these three groups, among the remaining five groups (core angiosperms), the relationship between the three broadest of these groups (magnoliids, monocots, and eudicots) remains unclear. Zeng and colleagues (Fig. 1) describe four competing schemes.[18] Of these, eudicots and monocots are the largest and most diversified, with ~ 75% and 20% of angiosperm species, respectively. Some analyses make the magnoliids the first to diverge, others the monocots.[19]Ceratophyllum seems to group with the eudicots rather than with the monocots. The 2016 Angiosperm Phylogeny Group revision (APG IV) retained the overall higher order relationship described in APG III.[13]

Fossilized spores suggest that higher plants (embryophytes) have lived on land for at least 475 million years.[20] Early land plants reproduced sexually with flagellated, swimming sperm, like the green algae from which they evolved. An adaptation to terrestrialization was the development of upright meiosporangia for dispersal by spores to new habitats, this feature is lacking in the descendants of their nearest algal relatives, the Charophycean green algae. A later terrestrial adaptation took place with retention of the delicate, avascular sexual stage, the gametophyte, within the tissues of the vascular sporophyte, this occurred by spore germination within sporangia rather than spore release, as in non-seed plants. A current example of how this might have happened can be seen in the precocious spore germination in Selaginella, the spike-moss, the result for the ancestors of angiosperms was enclosing them in a case, the seed. The first seed bearing plants, like the ginkgo, and conifers (such as pines and firs), did not produce flowers. The pollen grains (male gametophytes) of Ginkgo and cycads produce a pair of flagellated, mobile sperm cells that "swim" down the developing pollen tube to the female and her eggs.

The apparently sudden appearance of nearly modern flowers in the fossil record initially posed such a problem for the theory of evolution that Charles Darwin called it an "abominable mystery".[21] However, the fossil record has considerably grown since the time of Darwin, and recently discovered angiosperm fossils such as Archaefructus, along with further discoveries of fossil gymnosperms, suggest how angiosperm characteristics may have been acquired in a series of steps. Several groups of extinct gymnosperms, in particular seed ferns, have been proposed as the ancestors of flowering plants, but there is no continuous fossil evidence showing exactly how flowers evolved, some older fossils, such as the upper TriassicSanmiguelia, have been suggested. Based on current evidence, some propose that the ancestors of the angiosperms diverged from an unknown group of gymnosperms in the Triassic period (245–202 million years ago). Fossil angiosperm-like pollen from the Middle Triassic (247.2–242.0 Ma) suggests an older date for their origin.[22] A close relationship between angiosperms and gnetophytes, proposed on the basis of morphological evidence, has more recently been disputed on the basis of molecular evidence that suggest gnetophytes are instead more closely related to other gymnosperms.[citation needed]

The evolution of seed plants and later angiosperms appears to be the result of two distinct rounds of whole genome duplication events,[23] these occurred at 319 million years ago and 192 million years ago. Another possible whole genome duplication event at 160 million years ago perhaps created the ancestral line that led to all modern flowering plants.[24] That event was studied by sequencing the genome of an ancient flowering plant, Amborella trichopoda,[25] and directly addresses Darwin's "abominable mystery."

The earliest known macrofossil confidently identified as an angiosperm, Archaefructus liaoningensis, is dated to about 125 million years BP (the Cretaceous period),[26] whereas pollen considered to be of angiosperm origin takes the fossil record back to about 130 million years BP. However, one study has suggested that the early-middle Jurassic plant Schmeissneria, traditionally considered a type of ginkgo, may be the earliest known angiosperm, or at least a close relative;[27] in addition, circumstantial chemical evidence has been found for the existence of angiosperms as early as 250 million years ago. Oleanane, a secondary metabolite produced by many flowering plants, has been found in Permian deposits of that age together with fossils of gigantopterids.[28][29] Gigantopterids are a group of extinct seed plants that share many morphological traits with flowering plants, although they are not known to have been flowering plants themselves.[citation needed]

In 2013 flowers encased in amber were found and dated 100 million years before present, the amber had frozen the act of sexual reproduction in the process of taking place. Microscopic images showed tubes growing out of pollen and penetrating the flower's stigma, the pollen was sticky, suggesting it was carried by insects.[30]

The great angiosperm radiation, when a great diversity of angiosperms appears in the fossil record, occurred in the mid-Cretaceous (approximately 100 million years ago). However, a study in 2007 estimated that the division of the five most recent (the genus Ceratophyllum, the family Chloranthaceae, the eudicots, the magnoliids, and the monocots) of the eight main groups occurred around 140 million years ago.[35] By the late Cretaceous, angiosperms appear to have dominated environments formerly occupied by ferns and cycadophytes, but large canopy-forming trees replaced conifers as the dominant trees only close to the end of the Cretaceous 66 million years ago or even later, at the beginning of the Tertiary.[36] The radiation of herbaceous angiosperms occurred much later.[37] Yet, many fossil plants recognizable as belonging to modern families (including beech, oak, maple, and magnolia) had already appeared by the late Cretaceous.

It has been proposed that the swift rise of angiosperms to dominance was facilitated by a reduction in their genome size, during the early Cretaceous period, only angiosperms underwent rapid genome downsizing, while genome sizes of ferns and gymnosperms remained unchanged. Smaller genomes–and smaller nuclei–allow for faster rates of cell division and smaller cells. Thus, species with smaller genomes can pack more, smaller cells–in particular veins and stomata–into a given leaf volume. Genome downsizing therefore facilitated higher rates of leaf gas exchange (transpiration and photosynthesis) and faster rates of growth, this would have countered some of the negative physiological effects of genome duplications, facilitated increased uptake of carbon dioxide despite concurrent declines in atmospheric CO2 concentrations, and allowed the flowering plants to outcompete other land plants.[38]

It is generally assumed that the function of flowers, from the start, was to involve mobile animals in their reproduction processes, that is, pollen can be scattered even if the flower is not brightly colored or oddly shaped in a way that attracts animals; however, by expending the energy required to create such traits, angiosperms can enlist the aid of animals and, thus, reproduce more efficiently.

Island genetics provides one proposed explanation for the sudden, fully developed appearance of flowering plants. Island genetics is believed to be a common source of speciation in general, especially when it comes to radical adaptations that seem to have required inferior transitional forms. Flowering plants may have evolved in an isolated setting like an island or island chain, where the plants bearing them were able to develop a highly specialized relationship with some specific animal (a wasp, for example), such a relationship, with a hypothetical wasp carrying pollen from one plant to another much the way fig wasps do today, could result in the development of a high degree of specialization in both the plant(s) and their partners. Note that the wasp example is not incidental; bees, which, it is postulated, evolved specifically due to mutualistic plant relationships, are descended from wasps.[39]

Animals are also involved in the distribution of seeds. Fruit, which is formed by the enlargement of flower parts, is frequently a seed-dispersal tool that attracts animals to eat or otherwise disturb it, incidentally scattering the seeds it contains (see frugivory), although many such mutualistic relationships remain too fragile to survive competition and to spread widely, flowering proved to be an unusually effective means of reproduction, spreading (whatever its origin) to become the dominant form of land plant life.

Flower ontogeny uses a combination of genes normally responsible for forming new shoots,[40] the most primitive flowers probably had a variable number of flower parts, often separate from (but in contact with) each other. The flowers tended to grow in a spiral pattern, to be bisexual (in plants, this means both male and female parts on the same flower), and to be dominated by the ovary (female part), as flowers evolved, some variations developed parts fused together, with a much more specific number and design, and with either specific sexes per flower or plant or at least "ovary-inferior".

Flower evolution continues to the present day; modern flowers have been so profoundly influenced by humans that some of them cannot be pollinated in nature. Many modern domesticated flower species were formerly simple weeds, which sprouted only when the ground was disturbed, some of them tended to grow with human crops, perhaps already having symbiotic companion plant relationships with them, and the prettiest did not get plucked because of their beauty, developing a dependence upon and special adaptation to human affection.[41]

A few paleontologists have also proposed that flowering plants, or angiosperms, might have evolved due to interactions with dinosaurs. One of the idea's strongest proponents is Robert T. Bakker. He proposes that herbivorous dinosaurs, with their eating habits, provided a selective pressure on plants, for which adaptations either succeeded in deterring or coping with predation by herbivores.[42]

In August 2017, scientists presented a detailed description and 3D model image of what the first flower possibly looked like, and presented the hypothesis that it may have lived about 140 million years ago.[43][44]

A Bayesian analysis of 52 angiosperm taxa suggested that the crown group of angisperms evolved between 178 million years ago and 198 million years ago.[45]

The number of species of flowering plants is estimated to be in the range of 250,000 to 400,000.[46][47][48] This compares to around 12,000 species of moss[49] or 11,000 species of pteridophytes,[50] showing that the flowering plants are much more diverse. The number of families in APG (1998) was 462; in APG II[12] (2003) it is not settled; at maximum it is 457, but within this number there are 55 optional segregates, so that the minimum number of families in this system is 402. In APG III (2009) there are 415 families.[13][51]

The diversity of flowering plants is not evenly distributed. Nearly all species belong to the eudicot (75%), monocot (23%), and magnoliid (2%) clades, the remaining 5 clades contain a little over 250 species in total; i.e. less than 0.1% of flowering plant diversity, divided among 9 families. The 43 most-diverse of 443 families of flowering plants by species,[52] in their APG circumscriptions, are

Of these, the Orchidaceae, Poaceae, Cyperaceae, Araceae, Bromeliaceae, Arecaceae, and Iridaceae are monocot families; Piperaceae, Lauraceae, and Annonaceae are magnoliid dicots; the rest of the families are eudicots.

Double fertilization refers to a process in which two sperm cells fertilize cells in the ovule. This process begins when a pollen grain adheres to the stigma of the pistil (female reproductive structure), germinates, and grows a long pollen tube. While this pollen tube is growing, a haploid generative cell travels down the tube behind the tube nucleus, the generative cell divides by mitosis to produce two haploid (n) sperm cells. As the pollen tube grows, it makes its way from the stigma, down the style and into the ovary. Here the pollen tube reaches the micropyle of the ovule and digests its way into one of the synergids, releasing its contents (which include the sperm cells), the synergid that the cells were released into degenerates and one sperm makes its way to fertilize the egg cell, producing a diploid (2n) zygote. The second sperm cell fuses with both central cell nuclei, producing a triploid (3n) cell, as the zygote develops into an embryo, the triploid cell develops into the endosperm, which serves as the embryo's food supply. The ovary will now develop into a fruit and the ovule will develop into a seed.

As the development of embryo and endosperm proceeds within the embryo sac, the sac wall enlarges and combines with the nucellus (which is likewise enlarging) and the integument to form the seed coat. The ovary wall develops to form the fruit or pericarp, whose form is closely associated with type of seed dispersal system.[54]

Frequently, the influence of fertilization is felt beyond the ovary, and other parts of the flower take part in the formation of the fruit, e.g., the floral receptacle in the apple, strawberry, and others.[citation needed]

The character of the seed coat bears a definite relation to that of the fruit, they protect the embryo and aid in dissemination; they may also directly promote germination. Among plants with indehiscent fruits, in general, the fruit provides protection for the embryo and secures dissemination; in this case, the seed coat is only slightly developed. If the fruit is dehiscent and the seed is exposed, in general, the seed-coat is well developed, and must discharge the functions otherwise executed by the fruit.[citation needed]

Flowering plants generate gametes using a specialized cell division called meiosis. Meiosis takes place in the ovule (a structure within the ovary that is located within the pistil at the center of the flower) (see diagram labeled "Angiosperm lifecycle"). A diploid cell (megaspore mother cell) in the ovule undergoes meiosis (involving two successive cell divisions) to produce four cells (megaspores) with haploid nuclei.[55] One of these four cells (megaspore) then undergoes three successive mitotic divisions to produce an immature embryo sac (megagametophyte) with eight haploid nuclei. Next, these nuclei are segregated into separate cells by cytokinesis to producing 3 antipodal cells, 2 synergid cells and an egg cell. Two polar nuclei are left in the central cell of the embryo sac.[citation needed]

Pollen is also produced by meiosis in the male anther (microsporangium), during meiosis, a diploid microspore mother cell undergoes two successive meiotic divisions to produce 4 haploid cells (microspores or male gametes). Each of these microspores, after further mitoses, becomes a pollen grain (microgametophyte) containing two haploid generative (sperm) cells and a tube nucleus. When a pollen grain makes contact with the female stigma, the pollen grain forms a pollen tube that grows down the style into the ovary; in the act of fertilization, a male sperm nucleus fuses with the female egg nucleus to form a diploid zygote that can then develop into an embryo within the newly forming seed. Upon germination of the seed, a new plant can grow and mature.[citation needed]

The adaptive function of meiosis is currently a matter of debate. A key event during meiosis in a diploid cell is the pairing of homologous chromosomes and homologous recombination (the exchange of genetic information) between homologous chromosomes, this process promotes the production of increased genetic diversity among progeny and the recombinational repair of damages in the DNA to be passed on to progeny. To explain the adaptive function of meiosis in flowering plants, some authors emphasize diversity[56] and others emphasize DNA repair.[57]

Apomixis (reproduction via asexually formed seeds) is found naturally in about 2.2% of angiosperm genera [58] One type of apomixis, gametophytic apomixis found in a dandelion species [59] involves formation of an unreduced embryo sac due to incomplete meiosis (apomeiosis) and development of an embryo from the unreduced egg inside the embryo sac, without fertilization (parthenogenesis).[citation needed]

In some parts of the world, certain single species assume paramount importance because of their variety of uses, for example the coconut (Cocos nucifera) on Pacific atolls, and the olive (Olea europaea) in the [[Mediterranean region|Mediterranean region[citation needed]]].

Flowering plants also provide economic resources in the form of wood, paper, fiber (cotton, flax, and hemp, among others), medicines (digitalis, camphor), decorative and landscaping plants, and many other uses. The main area in which they are surpassed by other plants — namely, coniferous trees (Pinales), which are non-flowering (gymnosperms) — is timber and paper production.[60]

^Brown R., Character and description of Kingia, a new genus of plants found on the southwest coast of New Holland: with observations on the structure of its unimpregnated ovulum; and on the female flower of Cycadeae and Coniferae, in: King P.P. (Ed.) Narrative of a Survey of the Intertropical and western coasts of Australia, performed between years 1818 and 1822. John Murray, London, 1827, vol. 2., pp. 534–565, [1].

1.
Holocene
–
The Holocene is the geological epoch that began after the Pleistocene at approximately 11,700 years before present. The term Recent has often used as an exact synonym of Holocene. The Holocene is part of the Quaternary period and its name comes from the Ancient Greek words ὅλος and καινός, meaning entirely recent. It has been identified with the current warm period, known as MIS1, given these, a new term, Anthropocene, is specifically proposed and used informally only for the very latest part of modern history involving significant human impact. It is accepted by the International Commission on Stratigraphy that the Holocene started approximately 11,700 years ago, the epoch follows the Pleistocene and the last glacial period. The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations, Preboreal, Boreal, Atlantic, Subboreal and they find a general correspondence across Eurasia and North America, though the method was once thought to be of no interest. The scheme was defined for Northern Europe, but the changes were claimed to occur more widely. The periods of the include a few of the final pre-Holocene oscillations of the last glacial period. Paleontologists have not defined any faunal stages for the Holocene, if subdivision is necessary, periods of human technological development, such as the Mesolithic, Neolithic, and Bronze Age, are usually used. However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world, climatically, the Holocene may be divided evenly into the Hypsithermal and Neoglacial periods, the boundary coincides with the start of the Bronze Age in Europe. According to some scholars, a division, the Anthropocene, has now begun. Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years, however, ice melt caused world sea levels to rise about 35 m in the early part of the Holocene. The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea, Holocene marine fossils are known, for example, from Vermont and Michigan. Other than higher-latitude temporary marine incursions associated with depression, Holocene fossils are found primarily in lakebed, floodplain. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely tectonic uplift of non-glacial origin, post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea. The region continues to rise, still causing weak earthquakes across Northern Europe, the equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries. Climate has been stable over the Holocene. It appears that this was influenced by the glacial ice remaining in the Northern Hemisphere until the later date

2.
Megaannum
–
A year is the orbital period of the Earth moving in its orbit around the Sun. Due to the Earths axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the globe, four seasons are recognized, spring, summer, autumn. In tropical and subtropical regions several geographical sectors do not present defined seasons, but in the seasonal tropics, a calendar year is an approximation of the number of days of the Earths orbital period as counted in a given calendar. The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a year of 366 days, as do the Julian calendars. For the Gregorian calendar the average length of the year across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a to represent a year of either 365 or 366 days, in English, the abbreviations y and yr are commonly used. In astronomy, the Julian year is a unit of time, it is defined as 365.25 days of exactly 86400 seconds, totalling exactly 31557600 seconds in the Julian astronomical year. The word year is used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year. Similarly, year can mean the period of any planet, for example. The term can also be used in reference to any long period or cycle, west Saxon ġēar, Anglian ġēr continues Proto-Germanic *jǣran. Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, all the descendants of the Proto-Indo-European noun *yeh₁rom year, season. Cognates also descended from the same Proto-Indo-European noun are Avestan yārǝ year, Greek ὥρα year, season, period of time, Old Church Slavonic jarŭ, Latin annus is from a PIE noun *h₂et-no-, which also yielded Gothic aþn year. Both *yeh₁-ro- and *h₂et-no- are based on verbal roots expressing movement, *h₁ey- and *h₂et- respectively, the Greek word for year, ἔτος, is cognate with Latin vetus old, from the PIE word *wetos- year, also preserved in this meaning in Sanskrit vat-sa- yearling and vat-sa-ras year. Derived from Latin annus are a number of English words, such as annual, annuity, anniversary, etc. per annum means each year, anno Domini means in the year of the Lord. No astronomical year has an number of days or lunar months. Financial and scientific calculations often use a 365-day calendar to simplify daily rates, in the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a year there are 366 days

3.
Precambrian
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The Precambrian is the earliest period of Earths history, set before the current Phanerozoic Eon. The Precambrian is a supereon that is subdivided into three eons of the time scale. It spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, the Precambrian accounts for 89% of geologic time. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earths history, the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, and fossils from that time are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion. A stable crust was apparently in place by 4,412 Ma, the term Precambrian is recognized by the International Commission on Stratigraphy as a general term including the Archean and Proterozoic eons. It is still used by geologists and paleontologists for general discussions not requiring the more specific eon names and it was briefly called the Cryptozoic eon. A specific date for the origin of life has not been determined, carbon found in 3.8 billion year old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have found in Western Australia. Probable fossils 100 million years older have been found in the same area, there is a fairly solid record of bacterial life throughout the remainder of the Precambrian. The oldest fossil evidence from that era of such complex life comes from the Lantian formation of the Ediacarian period, a very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota, hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic era. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale. The explosion in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life, while land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Evidence of the details of plate motions and other activity in the Precambrian has been poorly preserved. It is generally believed that small proto-continents existed prior to 4280 Ma, the supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch, one of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a Snowball Earth. The atmosphere of the early Earth is not well understood, most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and was lacking in free oxygen

4.
Cambrian
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The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya and its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, as a result, our understanding of the Cambrian biology surpasses that of some later periods. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia, the seas were relatively warm, and polar ice was absent for much of the period. The United States Federal Geographic Data Committee uses a barred capital C ⟨Є⟩ character similar to the capital letter Ukrainian Ye ⟨Є⟩ to represent the Cambrian Period, the proper Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH BAR. Despite the long recognition of its distinction from younger Ordovician Period rocks and older Supereon Precambrian rocks, the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. Pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA, the stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain. The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period, the Cambrian is divided into four epochs and ten ages. Currently only two series and five stages are named and have a GSSP, because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian, Middle Cambrian and Furongian, rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian, each of the local epochs is divided into several stages. The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago, the lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites. The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier and this formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago quickly gained favour, though the used to obtain this number are now considered to be unsuitable. A more precise date using modern radiometric dating yield a date of 541 ±0.3 million years ago, most continental land was clustered in the Southern Hemisphere at this time, but was drifting north. Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian, the sea levels fluctuated somewhat, suggesting there were ice ages, associated with pulses of expansion and contraction of a south polar ice cap. In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into a epicontinental sea, the Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents

5.
Ordovician
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The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Mya. Lapworth recognized that the fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods. It received international sanction in 1960, when it was adopted as a period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, invertebrates, namely molluscs and arthropods, dominated the oceans. The Great Ordovician Biodiversification Event considerably increased the diversity of life, fish, the worlds first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land, about 100 times as many meteorites struck the Earth during the Ordovician compared with today. The Ordovician Period began with a major extinction called the Cambrian–Ordovician extinction event and it lasted for about 42 million years and ended with the Ordovician–Silurian extinction event, about 443.8 Mya which wiped out 60% of marine genera. The dates given are recent radiometric dates and vary slightly from those found in other sources and this second period of the Paleozoic era created abundant fossils that became major petroleum and gas reservoirs. The boundary chosen for the beginning of both the Ordovician Period and the Tremadocian stage is highly significant and it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species. The base of the Tremadocian allows scientists to relate these species not only to each other and this makes it easier to place many more species in time relative to the beginning of the Ordovician Period. A number of terms have been used to subdivide the Ordovician Period. In 2008, the ICS erected an international system of subdivisions. There exist Baltoscandic, British, Siberian, North American, Australian, the Ordovician Period in Britain was traditionally broken into Early, Middle and Late epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, the Floian corresponds to the lower Arenig, the Arenig continues until the early Darriwilian, subsuming the Dapingian. The Llanvirn occupies the rest of the Darriwilian, and terminates with it at the base of the Late Ordovician. The Sandbian represents the first half of the Caradoc, the Caradoc ends in the mid-Katian, during the Ordovician, the southern continents were collected into Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole, the small continent Avalonia separated from Gondwana and began to move north towards Baltica and Laurentia, opening the Rheic Ocean between Gondwana and Avalonia

6.
Silurian
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The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway

7.
Devonian
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The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, England, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician. The first ammonites, species of molluscs, appeared, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers

8.
Carboniferous
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The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period,298.9 Mya. The name Carboniferous means coal-bearing and derives from the Latin words carbō and ferō, and was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the system names to be employed. The Carboniferous is often treated in North America as two periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial life was established by the Carboniferous period. Amphibians were the dominant land vertebrates, of one branch would eventually evolve into amniotes. Arthropods were also common, and many were much larger than those of today. Vast swaths of forest covered the land, which would eventually be laid down, the atmospheric content of oxygen also reached their highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. A major marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred in the middle of the period, the later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. In the United States the Carboniferous is usually broken into Mississippian and Pennsylvanian subperiods, the Silesian is roughly contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, and the Westphalian as the Coal Measures and Pennant Sandstone. There was also a drop in south polar temperatures, southern Gondwanaland was glaciated throughout the period and these conditions apparently had little effect in the deep tropics, where lush swamps, later to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major extinction, one that hit crinoids. This sea level drop and the unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation, the Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America, in the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, the Late Carboniferous Pangaea was shaped like an O. There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the O in the Carboniferous Pangaea, other minor oceans were shrinking and eventually closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean

9.
Permian
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The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, turtles, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms. During the Permian, all the Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, fungi, arthropods, the period saw a massive desert covering the interior of Pangaea

10.
Triassic
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The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago, to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era, both the start and end of the period are marked by major extinction events. Therapsids and archosaurs were the terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic, the vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, however, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another mass extinction, the Triassic-Jurassic extinction event. The Triassic is usually separated into Early, Middle, and Late Triassic Epochs, from the east, along the equator, the Tethys sea penetrated Pangaea, causing the Paleo-Tethys Ocean to be closed. Later in the mid-Triassic a similar sea penetrated along the equator from the west, the remaining shores were surrounded by the world-ocean known as Panthalassa. All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates, thus, the supercontinent Pangaea was rifting during the Triassic—especially late in that period—but had not yet separated. In North America, for example, marine deposits are limited to a few exposures in the west, thus Triassic stratigraphy is mostly based on organisms that lived in lagoons and hypersaline environments, such as Estheria crustaceans. At the beginning of the Mesozoic Era, Africa was joined with Earths other continents in Pangaea, Africa shared the supercontinents relatively uniform fauna which was dominated by theropods, prosauropods and primitive ornithischians by the close of the Triassic period. Late Triassic fossils are found throughout Africa, but are common in the south than north. The time boundary separating the Permian and Triassic marks the advent of an event with global impact. At Paleorrota geopark, located in Rio Grande do Sul, Brazil, in these formations, one of the earliest dinosaurs, Staurikosaurus, as well as the mammal ancestors Brasilitherium and Brasilodon have been discovered. The Triassic continental interior climate was hot and dry, so that typical deposits are red bed sandstones and evaporites. Pangaeas large size limited the effect of the global ocean, its continental climate was highly seasonal, with very hot summers. The strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons, the best studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event. On land, the vascular plants included the lycophytes, the dominant cycadophytes, ginkgophyta, ferns, horsetails

11.
Jurassic
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The Jurassic is a geologic period and system that spans 56.3 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles, the start of the period is marked by the major Triassic–Jurassic extinction event. The Jurassic is named after the Jura Mountains within the European Alps, by the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, on land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs, other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to a mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, the chronostratigraphic term Jurassic is directly linked to the Jura Mountains. The name Jura is derived from the Celtic root jor, which was Latinised into juria, the Jurassic period is divided into the Early Jurassic, Middle, and Late Jurassic epochs. The Jurassic System, in stratigraphy, is divided into the Lower Jurassic, Middle, the separation of the term Jurassic into three sections goes back to Leopold von Buch. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, the Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation, as in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed. In contrast, the North American Jurassic record is the poorest of the Mesozoic, the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, India, South America, Japan, Australasia. As the Jurassic proceeded, larger and more groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are well represented nor well studied in Africa. Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania, the Late Jurassic life of Tendaguru is very similar to that found in western North Americas Morrison Formation. During the Jurassic period, the primary living in the sea were fish

12.
Cretaceous
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The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls

13.
Paleogene
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The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera

14.
Neogene
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The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene, some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. During this period, mammals and birds continued to evolve into modern forms. Early hominids, the ancestors of humans, appeared in Africa near the end of the period, some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the ocean currents from the Pacific to the Atlantic ocean. The global climate cooled considerably over the course of the Neogene, the terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period. The continents in the Neogene were very close to their current positions, the Isthmus of Panama formed, connecting North and South America. The Indian subcontinent continued to collide with Asia, forming the Himalayas, sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America. The global climate became seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the current Ice Age began, marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the part of the period. Mammals and birds continued to be the dominant terrestrial vertebrates, the first hominids, the ancestors of humans, appeared in Africa and spread into Eurasia. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones, grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison. The Neogene traditionally ended at the end of the Pliocene Epoch, just before the definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to also include ongoing geological time in the Neogene, by dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The International Commission on Stratigraphy once proposed that the Quaternary be considered a sub-era of the Neogene, with a date of 2.58 Ma. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs, thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. Digital Atlas of Neogene Life for the Southeastern United States — by San Jose State University via Web Archive

15.
Magnolia virginiana
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Magnolia virginiana, most commonly known as sweetbay magnolia, or merely sweetbay, is a member of the magnolia family, Magnoliaceae. Magnolia virginiana is an evergreen or deciduous tree to 30 m tall, native to the lowlands, the original native range is thought to be from the eastern Gulf Coast to Long Island, New York. Whether it is deciduous or evergreen depends on climate, it is evergreen in areas with milder winters in the south of its range, the leaves are alternate, simple, with entire margins, 6-12 cm long, and 3-5 cm wide. The bark is smooth and gray, with the inner bark mildly scented, the flowers are creamy white, 8-14 cm diameter, with 6-15 petal-like tepals. The flowers carry a strong vanilla scent that can sometimes be noticed several hundred yards away. The fruit is an aggregate of follicles, 3-5 cm long, pinkish-red when mature. Magnolia virginiana is often grown as a tree in gardens. It is a tree for parks and large gardens, grown for its large, conspicuous, scented flowers, for its clean, attractive foliage. In warmer areas Magnolia virginiana is valued for its evergreen foliage, the English botanist and missionary John Banister collected Magnolia virginiana in the southeastern United States in 1678 and sent it to England, where it flowered for Bishop Henry Compton. These species include M. globosa, M. grandiflora, M. insignis, M. macrophylla, M. obovata, M. sieboldii, some of these hybrids have been given cultivar names and registered by the Magnolia Society. Flowers contain the neolignans 3, 5′-diallyl-2′, 4-dihydroxybiphenyl,4, 4′-diallyl-2, 3′-dihydroxybiphenyl ether,5, 5′-diallyl-2, 2′-dihydroxybiphenyl and 3, media related to Sweetbay Magnolia at Wikimedia Commons Magnolia virginiana images at bioimages. vanderbilt. edu Interactive Distribution Map of Magnolia virginiana

16.
Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate

17.
Plant
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Plants are mainly multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. The term is generally limited to the green plants, which form an unranked clade Viridiplantae. This includes the plants, conifers and other gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses and the green algae. Green plants have cell walls containing cellulose and obtain most of their energy from sunlight via photosynthesis by primary chloroplasts and their chloroplasts contain chlorophylls a and b, which gives them their green color. Some plants are parasitic and have lost the ability to produce amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although reproduction is also common. There are about 300–315 thousand species of plants, of which the great majority, green plants provide most of the worlds molecular oxygen and are the basis of most of Earths ecologies, especially on land. Plants that produce grains, fruits and vegetables form humankinds basic foodstuffs, Plants play many roles in culture. They are used as ornaments and, until recently and in variety, they have served as the source of most medicines. The scientific study of plants is known as botany, a branch of biology, Plants are one of the two groups into which all living things were traditionally divided, the other is animals. The division goes back at least as far as Aristotle, who distinguished between plants, which generally do not move, and animals, which often are mobile to catch their food. Much later, when Linnaeus created the basis of the system of scientific classification. Since then, it has become clear that the plant kingdom as originally defined included several unrelated groups, however, these organisms are still often considered plants, particularly in popular contexts. When the name Plantae or plant is applied to a group of organisms or taxon. The evolutionary history of plants is not yet settled. Those which have been called plants are in bold, the way in which the groups of green algae are combined and named varies considerably between authors. Algae comprise several different groups of organisms which produce energy through photosynthesis, most conspicuous among the algae are the seaweeds, multicellular algae that may roughly resemble land plants, but are classified among the brown, red and green algae. Each of these groups also includes various microscopic and single-celled organisms

18.
Embryophyte
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The Embryophyta are the most familiar group of green plants that form vegetation on earth. Living embryophytes include hornworts, liverworts, mosses, ferns, lycophytes, gymnosperms and flowering plants, the Embryophyta are informally called land plants because they live primarily in terrestrial habitats, while the related green algae are primarily aquatic. All are complex multicellular eukaryotes with specialized reproductive organs, the name derives from their innovative characteristic of nurturing the young embryo sporophyte during the early stages of its multicellular development within the tissues of the parent gametophyte. With very few exceptions, embryophytes obtain their energy by photosynthesis, the evolutionary origins of the embryophytes are discussed further below, but they are believed to have evolved from within a group of complex green algae during the Paleozoic era. Charales or the stoneworts may be the best living illustration of that developmental step, embryophytes are primarily adapted for life on land, although some are secondarily aquatic. Accordingly, they are called land plants or terrestrial plants. On a microscopic level, the cells of embryophytes are broadly similar to those of green algae and they are eukaryotic, with a cell wall composed of cellulose and plastids surrounded by two membranes. Embryophyte cells also generally have a central vacuole enclosed by a vacuolar membrane or tonoplast. In common with all groups of multicellular algae they have a cycle which involves alternation of generations. The mature sporophyte produces spores which grow into a gametophyte. Embryophytes have two related to their reproductive cycles which distinguish them from all other plant lineages. Firstly, their gametophytes produce sperm and eggs in multicellular structures and this second feature is the origin of the term embryophyte – the fertilized egg develops into a protected embryo, rather than dispersing as a single cell. In the bryophytes the sporophyte dependent on the gametophyte, while in all other embryophytes the sporophyte generation is dominant. Embryophytes also differ from algae by having metamers, metamers are repeated units of development, in which each unit derives from a single cell, but the resulting product tissue or part is largely the same for each cell. The whole organism is thus constructed from similar, repeating parts or metamers, accordingly, these plants are sometimes termed metaphytes and classified as the group Metaphyta. All green algae and land plants are now known to form an evolutionary lineage or clade. According to several molecular clock estimates the Viridiplantae split 1,200 million years ago to 725 million years ago into two clades, chlorophytes and streptophytes, the chlorophytes are considerably more diverse and were originally marine, although some groups have since spread into fresh water. The streptophyte algae are less diverse and adapted to fresh very early in their evolutionary history

19.
Spermatophyte
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The spermatophytes, also known as phanerogams or phenogamae, comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or land plants and these terms distinguished those plants with hidden sexual organs from those with visible sexual organs. In addition to the taxa listed above, the record contains evidence of many extinct taxa of seed plants. The so-called seed ferns were one of the earliest successful groups of land plants, glossopteris was the most prominent tree genus in the ancient southern supercontinent of Gondwana during the Permian period. A whole genome duplication event in the ancestor of seed plants occurred about 319 million years ago and this gave rise to a series of evolutionary changes that resulted in the origin of seed plants. A middle Devonian precursor to seed plants from Belgium has been identified predating the earliest seed plants by about 20 million years, runcaria, small and radially symmetrical, is an integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the mutlilobed integument and it is suspected that the extension was involved in anemophilous pollination. Runcaria sheds new light on the sequence of character acquisition leading to the seed, runcaria has all of the qualities of seed plants except for a solid seed coat and a system to guide the pollen to the seed. Seed-bearing plants were divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads, ginkgo. Older morphological studies believed in a relationship between the gnetophytes and the angiosperms, in particular based on vessel elements. However, molecular studies have shown a clade of gymnosperms. For example, one common proposed set of relationships is known as the hypothesis and looks like, However

20.
Basal angiosperms
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The basal angiosperms are the flowering plants which diverged from the lineage leading to most flowering plants. In particular, the most basal angiosperms were called the ANITA grade which is made up of Amborella, ANITA stands for Amborella, Nymphaeales and Illiciales, Trimeniaceae-Austrobaileya. The basal angiosperms are only a few hundred species, compared with hundreds of thousands of species of eudicots, monocots or magnoliids and they diverged from the ancestral angiosperm lineage before the five groups comprising the mesangiosperms diverged from each other. The exact relationships between Amborella, Nymphaeales and Austrobaileyales are not yet clear, a 2014 paper says that it presents the most convincing evidence to date that Amborella plus Nymphaeales together represent the earliest diverging lineage of extant angiosperms. Paleodicots is a name used by botanists to refer to angiosperms which are not monocots or eudicots. The paleodicots correspond to Magnoliidae sensu Cronquist 1981 and to Magnoliidae sensu Takhtajan 1980, some of the paleodicots share apparently plesiomorphic characters with monocots, e. g. scattered vascular bundles, trimerous flowers, and non-tricolpate pollen. The paleodicots are not a group and the term has not been widely adopted. Subsequent research has added Hydatellaceae to the paleodicots, the term paleoherb is another older term for flowering plants which are neither eudicots nor monocots

21.
Amborella
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Amborella is a monotypic genus of understory shrubs or small trees endemic to the main island, Grande Terre, of New Caledonia. The genus is the member of the family Amborellaceae and the order Amborellales and contains a single species. The family Amborellaceae is therefore endemic to New Caledonia, as well as the order Amborellales, Amborella is of great interest to plant systematists because molecular phylogenetic analyses consistently place the genus at or near the base of the flowering plant lineage. Amborella is a shrub or small tree up to 8 m high. It bears alternate or decussate, simple leaves without stipules. The leaves are two-ranked, with serrated or rippled margins. Amborella has xylem tissue that differs from that of most other flowering plants, the xylem of Amborella contains only tracheids, vessel elements are absent. Xylem of this form has long regarded as a primitive feature of flowering plants. This means that each plant produces either flowers or female flowers. At any one time, a plant produces only functionally staminate or functionally carpellate flowers. Staminate Amborella flowers do not have carpels, whereas the flowers have non-functional staminodes, structures resembling stamens in which no pollen develops. Plants may change from one reproductive morphology to the other, in one study, seven cuttings from a staminate plant produced, as expected, staminate flowers at their first flowering, but three of the seven produced carpellate flowers at their second flowering. The small, creamy white, flowers are arranged in inflorescences borne in the axils of foliage leaves, the inflorescences have been described as cymes, with up to three orders of branching, each branch being terminated by a flower. Each flower is subtended by bracts, the bracts transition into a perianth of undifferentiated tepals. The tepals typically are arranged in a spiral, but sometimes are whorled at the periphery, carpellate flowers are roughly 3 to 4 mm in diameter, with 7 or 8 tepals. There are 1 to 3 well-differentiated staminodes and a spiral of 4 to 8 free carpels, carpels bear green ovaries, they lack a style. They contain a single ovule with the micropyle directed downwards, staminate flowers are approximately 4 to 5 mm in diameter, with 6 to 15 tepals. These flowers bear 10 to 21 spirally arranged stamens, which become progressively smaller toward the center, the innermost may be sterile, amounting to staminodes

22.
Nymphaeales
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The Nymphaeales are an order of flowering plants, consisting of three families of aquatic plants, the Hydatellaceae, the Cabombaceae, and the Nymphaeaceae. It is one of the three orders of basal angiosperms, a grade of flowering plants. At least 10 morphological characters unite the Nymphaeales, the difference in species numbers is due almost entirely to the difficulty of delineating species in the genus Nymphaea. All of the species are rhizomatous aquatic herbs with a broad base and large. The fossil record consists especially of seeds, but also pollen, stems, leaves and it extends back to the Cretaceous. The crown group of the Nymphaeales has been estimated to be about 112 million years old, some have suggested that this age might be too old. The aquatic plant fossil Archaefructus possibly belongs to this group, the Nymphaeales currently include three families and about 70 to 90 species. This order was not part of the APG II systems 2003 plant classification, the APG III system did separate the Cabombaceae from the Nymphaeaceae and placed them in the order Nymphaeales together with the Hydatellaceae. This familyHydatellaceae was placed among the monocots in previous systems, but a 2007 study found that the belongs to the Nymphaeales. Some earlier systems, such as Cronquists system of 1981, often included the Ceratophyllaceae and Nelumbonaceae in the Nymphaeales, although, the Takhtajan system of 1980 separated the Nelumbonales, the new order was retained alongside the Nymphaeales in the superorder Nymphaeanae. The Cronquist system placed the Nymphaeales in subclass Magnoliidae, in class Magnoliopsida, in addition, Cronquist included the Ceratophyllaceae and split the family Barclayaceae from the Nymphaeaceae. Under the APG II system, the family Cambombaceae was included within the Nymphaeaceae, as of APG III, the two families are recognized separately. The Dahlgren system placed the Nymphaeales with the Piperales in superorder Nymphaeanae, thornes 1992 system placed the Nymphaeales as the sole order in the superorder Nymphaeanae within subclass Magnoliideae. Thomas N. Taylor, Edith L. Taylor, and Michael Krings, paleobotany, The Biology and Evolution of Fossil Plants, Second Edition. ISBN 978-0-12-373972-8 Nymphaeales At, Angiosperm Phylogeny Website At, botanical databases At, Plant Science At, Missouri Botanical Garden Data related to Nymphaeales at Wikispecies

23.
Mesangiospermae
–
Mesangiospermae is a group of flowering plants, informally called mesangiosperms. They are one of two clades of angiosperms. It is a name created under the rules of the PhyloCode system of phylogenetic nomenclature, there are about 350,000 species of mesangiosperms. The mesangiosperms contain about 99. 95% of the plants, assuming that there are about 175 species not in this group. While such a clade with a similar circumscription exists in the APG III system, besides the mesangiosperms, the other groups of flowering plants are Amborellales, Nymphaeales, and Austrobaileyales. These constitute a paraphyletic grade called basal angiosperms, the order names, ending in -ales are used here without reference to taxonomic rank because these groups contain only one order. The name Mesangiospermae is a branch-modified node-based name in phylogenetic nomenclature and it is defined as the most inclusive crown clade containing Platanus occidentalis, but not Amborella trichopoda, Nymphaea odorata, or Austrobaileya scandens. It is sometimes written as even though this is not required by the PhyloCode. The clademark slash indicates that the term is intended as phylogenetically defined, in molecular phylogenetic studies, the mesangiosperms are always strongly supported as a monophyletic group. There is no distinguishing characteristic which is found in all mature mesangiosperms, nevertheless, the mesangiosperms are recognizable in the earliest stage of embryonic development. The ovule contains a megagametophyte, also known as an embryo sac, the antipodal cells are persistent, and the endosperm is triploid. The oldest known fossils of flowering plants are fossil mesangiosperms from the Hauterivian stage of the Cretaceous period, molecular clock comparisons of DNA sequences indicate that the mesangiosperms originated between 140 and 150 Mya near the beginning of the Cretaceous period. This was about 25 Ma after the origin of the angiosperms in the mid-Jurassic, by 135Mya, the mesangioisperms had radiated into 5 groups, Chloranthales, Magnoliids, Monocots, Ceratophyllales, and Eudicots. The radiation into 5 groups probably occurred in about 4 million years, because the interval of this radiation is short in proportion to its age, it had long appeared that the 5 groups of mesangiosperms had arisen simultaneously. The mesangiosperms were shown as an unresolved pentatomy in phylogenetic trees, in 2007, two studies attempted to resolve the phylogenetic relationships among these 5 groups by comparing large portions of their chloroplast genomes. These studies agreed on the most likely phylogeny for the mesangiosperms, in this phylogeny, the monocots are sister to the clade. However, this result is not strongly supported, the approximately unbiased topology test showed that some of the other possible positions of the monocots had more than 5% probability of being correct. The major weakness of these 2 studies was the number of species whose DNA was being used in the phylogenetic analysis,45 in one study and 64 in the other

24.
Magnoliids
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Magnoliids are a group of flowering plants. Until recently, the group included about 9,000 species, including magnolias, nutmeg, bay laurel, cinnamon, avocado, black pepper, tulip tree and that group is characterized by trimerous flowers, pollen with one pore, and usually branching-veined leaves. Magnoliidae is the name of a subclass, and magnoliids is an informal name that does not conform to the International Code of Nomenclature for algae, fungi. The circumscription of a subclass will vary with the system being used. The only requirement is that it must include the family Magnoliaceae, the informal name magnoliids is used by some researchers to avoid the confusion that recently surrounds the name Magnoliidae. More recently, the group has been redefined under the PhyloCode as a clade comprising the Canellales, Laurales, Magnoliales. Chase & Reveal have proposed, Magnoliidae as the used for the entire group of flowering plants. The APG III and its predecessor systems did not originally use formal botanical names above the rank of order, under those systems, larger clades were usually referred to by informal names, such as magnoliids or magnoliid complex. The formal name in Linnean nomenclature was specified in a separate APG publication as the existing name Magnolianae Takht, the APG III recognizes a clade within the angiosperms for the magnoliids. The circumscription is, The clade includes most of the groups of the angiosperms. This clade was formally named Magnoliidae in 2007 under provisions of the PhyloCode, the Cronquist system used the name Magnoliidae for one of six subclasses. In their systems, the name Magnoliidae is used for a larger group including all dicotyledons. This is also the case in some of the derived from the Cronquist system. Dahlgren divided his Magnolianae into ten orders, more than other systems of the time and this revised system diverges from the Cronquist system, but agrees more closely with the circumscription later published under APG II. Comparison of classification systems is often difficult, two authors may also describe the same group with nearly identical composition, but each may then apply a different name to that group or place the group at a different taxonomic rank. For example, the composition of Cronquists subclass Magnoliidae is nearly the same as Thornes superorder Magnolianae, because of these difficulties and others, the synoptic table below imprecisely compares the definition of magnoliid groups in the systems of four authors. For each system, only orders are named in the table, all orders included by a particular author are listed and linked in that column. When a taxon is not included by that author, but was included by an author in another column, the sequence of each system has been altered from its publication in order to pair corresponding taxa between columns

25.
Chloranthaceae
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Chloranthaceae /ˌklɔərænˈθeɪʃiː/ is a family of flowering plants, the only family in the order Chloranthales. It is not closely related to any family of flowering plants. They are woody or weakly woody plants occurring in Southeast Asia, the Pacific, Madagascar, Central and South America, the family consists of four extant genera, totalling about 77 known species according to Christenhusz and Byng in 2016. Some species are used in traditional medicine, Chloranthaceae species are aromatic plants with soft wood, having opposite, evergreen leaves with distinctive serrate margins and interpetiolar stipules. The flowers are inconspicuous, and arranged in inflorescences, petals are absent in this family, and sometimes so are sepals. The flowers can be hermaphrodite or of separate sexes. The fruit is drupe-like, consisting of one carpel, Chloranthaceae have been recognised as a family in most classifications but without clear relatives. Molecular systematic studies have shown that it is not closely related to any family and is among the early-diverging lineages in the angiosperms. In particular, it is neither a eudicot nor a monocot, fossils assigned to Chloranthaceae, or closely related to the family, are among the oldest angiosperms known. The APG II system left the family unplaced as to order, the cladogram below, from the APG IV system, shows the Chloranthales in a trichotomy with the magnoliids and the monocot-Ceratophyllales-dicot clade. Earlier the order was grouped with magnoliids, but studies in 2014 did not support this placement, as of June 2016, four extant genera are recognized, Ascarina J. R. Forst. Sarcandra Gardner The extinct genus Chloranthistemon also belongs to this family, the Cronquist system assigned the family to the order Piperales in subclass Magnoliidae in class Magnoliopsida of division Magnoliophyta. The Thorne system placed it in the order Magnoliales, which was assigned to superorder Magnolianae in subclass Magnoliideae, the Dahlgren system raised the family to be its own order Chloranthales, which was assigned to superorder Magnolianae in subclass Magnoliideae, in class Magnoliopsida. Chloranthaceae in L. Watson and M. J. Dallwitz The families of flowering plants, descriptions, illustrations, andes Trees NCBI Taxonomy Browser Images of Chloranthus Flavons art gallery, Chloranthaceae Image of Chloranthus oldhamii Image of Chloranthus serratus Images of Sarcandra glabra

26.
Monocotyledon
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Monocotyledons, commonly referred to as monocots, are flowering plants whose seeds typically contain only one embryonic leaf, or cotyledon. However, molecular research has shown that while the monocots form a monophyletic group or clade. Monocots have almost always recognized as a group, but with various taxonomic ranks. The APG III system of 2009 recognises a clade called monocots, the monocots include about 60,000 species. The largest family in this group by number of species are the orchids, about half as many species belong to the true grasses, which are economically the most important family of monocots. In agriculture the majority of the biomass produced comes from monocots and these include not only major grains, but also forage grasses, sugar cane, and the bamboos. Other economically important monocot crops include various palms, bananas, gingers and their relatives, turmeric and cardamom, asparagus and the onions and garlic family. Additionally most of the bulbs, plants cultivated for their blooms, such as lilies, daffodils, irises, amaryllis, cannas, bluebells. The monocots or monocotyledons have, as the name implies, a single cotyledon, or embryonic leaf, from a diagnostic point of view the number of cotyledons is neither a particularly useful characteristic, nor is it completely reliable. Nevertheless, monocots are sufficiently distinctive that there has rarely been disagreement as to membership of this group, however, morphological features that reliably characterise major clades are rare. Thus monocots are distinguishable from other angiosperms both in terms of their uniformity and diversity, although largely herbaceous, some arboraceous monocots reach great height, length and mass. The latter include agaves, palms, pandans, and bamboos and this creates challenges in water transport that monocots deal with in various ways. Some such as species of Yucca develop anomalous secondary growth, while palm trees, the axis undergoes primary thickening, that progresses from internode to internode, resulting in a typical inverted conical shape of the basal primary axis. The limited conductivity also contributes to limited branching of the stems, despite these limitations a wide variety of adaptive growth forms has resulted from epiphytic orchids and bromeliads to submarine Alismatales and mycotrophic Burmanniaceae and Triuridaceae. Other monocots, particularly Poales have adopted a life form. Leaves The cotyledon, the primordial Angiosperm leaf consists of a proximal leaf base or hypophyll, in moncots the hypophyll tends to be the dominant part in contrast to other angiosperms. Mature monocot leaves are narrow and linear, forming a sheathing around the stem at its base. There is usually only one leaf per node because the leaf base encompasses more than half the circumference, the evolution of this monocot characteristic has been attributed to developmental differences in early zonal differentiation rather than meristem activity

27.
Ceratophyllum
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Ceratophyllum is a cosmopolitan genus of flowering plants including four accepted species in 2016, commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. It is the genus in the family Ceratophyllaceae, itself the only family in the order Ceratophyllales. They are usually called coontails or hornworts, although hornwort is also used for unrelated plants of the division Anthocerotophyta, Ceratophyllum grows completely submerged, usually, though not always, floating on the surface, and does not tolerate drought. The plant stems can reach 1–3 m in length, at intervals along nodes of the stem they produce rings of bright green leaves, which are narrow and often much-branched. The forked leaves are brittle and stiff to the touch in some species, the plants have no roots at all, but sometimes they develop modified leaves with a rootlike appearance, which anchor the plant to the bottom. The flowers are small and inconspicuous, with the male and female flowers on the same plant, hornwort plants float in great numbers just under the surface. They offer excellent protection to fish-spawn, but also to snails that are infected with Bilharzia, because of their appearance and their high oxygen production, they are often used in freshwater aquaria. Ceratophyllum is considered enough to warrant its own family, Ceratophyllaceae. Some early molecular phylogenies suggested it was the group to all other angiosperms. The APG III system placed the family in its own order, the APG IV system accepts the phylogeny shown below, The division of the genus into species is not completely settled. More than 30 species have been described, but many are probably just variants of these widely accepted species. - widespread in places though not all countries Ceratophyllum platyacanthum Cham. - Scattered locations in Germany, Hungary, France, Russia, China, Japan, Korea Ceratophyllum submersum L. Ceratophyllaceae of Mongolia in FloraGREIF

28.
Eudicots
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The eudicots, Eudicotidae or eudicotyledons are a monophyletic clade of flowering plants that had been called tricolpates or non-magnoliid dicots by previous authors. The close relationships among flowering plants with tricolpate pollen grains was initially seen in studies of shared derived characters. These plants have a trait in their pollen grains of exhibiting three colpi or grooves paralleling the polar axis. Later molecular evidence confirmed the basis for the evolutionary relationships among flowering plants with tricolpate pollen grains. The term means true dicotyledons, as it contains the majority of plants that have been considered dicots and have characteristics of the dicots, the term eudicots has subsequently been widely adopted in botany to refer to one of the two largest clades of angiosperms, monocots being the other. The remaining angiosperms are sometimes referred to as basal angiosperms or paleodicots, the other name for the eudicots is tricolpates, a name which refers to the grooved structure of the pollen. Members of the group have tricolpate pollen, or forms derived from it and these pollens have three or more pores set in furrows called colpi. In contrast, most of the seed plants produce monosulcate pollen. The name tricolpates is preferred by some botanists to avoid confusion with the dicots, numerous familiar plants are eudicots, including many common food plants, trees, and ornamentals. Most leafy trees of midlatitudes also belong to eudicots, with exceptions being magnolias and tulip trees which belong to magnoliids, and Ginkgo biloba. The name eudicots is used in the APG system, of 1998 and it is applied to a clade, a monophyletic group, which includes most of the dicots. The eudicots can be divided into two groups, the basal eudicots and the core eudicots, basal eudicot is an informal name for a paraphyletic group. The core eudicots are a monophyletic group, a 2010 study suggested the core eudicots can be divided into two clades, Gunnerales and a clade called Pentapetalae, comprising all the remaining core eudicots

29.
Synonym (taxonomy)
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For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies. This name is no longer in use, it is now a synonym of the current scientific name which is Picea abies, unlike synonyms in other contexts, in taxonomy a synonym is not interchangeable with the name of which it is a synonym. In taxonomy, synonyms are not equals, but have a different status, for any taxon with a particular circumscription, position, and rank, only one scientific name is considered to be the correct one at any given time. A synonym cannot exist in isolation, it is always an alternative to a different scientific name, given that the correct name of a taxon depends on the taxonomic viewpoint used a name that is one taxonomists synonym may be another taxonomists correct name. Synonyms may arise whenever the same taxon is described and named more than once, independently. They may also arise when existing taxa are changed, as when two taxa are joined to one, a species is moved to a different genus. To the general user of scientific names, in such as agriculture, horticulture, ecology, general science. A synonym is a name that was used as the correct scientific name but which has been displaced by another scientific name. Thus Oxford Dictionaries Online defines the term as a name which has the same application as another. In handbooks and general texts, it is useful to have mentioned as such after the current scientific name. Synonyms used in this way may not always meet the strict definitions of the synonym in the formal rules of nomenclature which govern scientific names. Changes of scientific name have two causes, they may be taxonomic or nomenclatural, a name change may be caused by changes in the circumscription, position or rank of a taxon, representing a change in taxonomic, scientific insight. A name change may be due to purely nomenclatural reasons, that is, based on the rules of nomenclature, the earliest such name is called the senior synonym, while the later name is the junior synonym. One basic principle of zoological nomenclature is that the earliest correctly published name, synonyms are important because if the earliest name cannot be used, then the next available junior synonym must be used for the taxon. Objective synonyms refer to taxa with the type and same rank. For example, John Edward Gray published the name Antilocapra anteflexa in 1855 for a species of pronghorn, however, it is now commonly accepted that his specimen was an unusual individual of the species Antilocapra americana published by George Ord in 1815. Ords name thus takes precedence, with Antilocapra anteflexa being a subjective synonym. Objective synonyms are common at the level of genera, because for various reasons two genera may contain the type species, these are objective synonyms

30.
John Lindley
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John Lindley FRS was an English botanist, gardener and orchidologist. Born in Catton, near Norwich, England, John Lindley was one of four children of George, George Lindley was a nurseryman and pomologist and ran a commercial nursery garden. Although he had great knowledge, the undertaking was not profitable. As a boy he would assist in the garden and also collected wild flowers he found growing in the Norfolk countryside, Lindley was educated at Norwich School. He would have liked to go to university or to buy a commission in the army and he became Belgian agent for a London seed merchant in 1815. His first publication, in 1819, a translation of the Analyse du fruit of L. C. M. Lindley went to work at Banks’ house in London. He became acquainted with Joseph Sabine who grew a large assortment of roses and was the Secretary of the Horticultural Society of London and his employment came to an abrupt end with the death of Banks a few months later. One of Banks’ friends, a merchant called William Cattley, paid Lindley to draw. He also paid for the publication of “Digitalia Monographia”, in 1820, at the age of twenty-one, Lindley was elected a fellow of the Linnean Society of London. From 1821 to 1826 he published a work with coloured illustrations that he had painted himself, “Collectanea botanica or Figures and botanic Illustrations of rare. Many of these came from the family Orchidaceae with which he had a lifelong fascination. Lindley was appointed assistant secretary to the Royal Horticultural Society and its new garden at Chiswick in 1822, assistant secretary to the Horticultural Society since 1822, in 1829 Lindley was appointed to the chair of botany at University College, London, which he retained until 1860. He also played a part in having Charles Moore appointed as Director of the Sydney Botanical Gardens. He was a fellow of the Royal, Linnean and Geological Societies and he received the Royal Societys royal medal in 1857, and in 1853 became a corresponding member of the Institut de France. The Society’s historian, Harold R Fletcher, later described him as “ … the backbone of the Society and possibly the greatest servant it had ever had. ”Now with a steady income, in 1823 he married Sarah Freestone. They rented a house in rural Acton Green, a location convenient for the Society’s garden at Turnham Green, the Secretary of the Horticultural Society of London at that time was Joseph Sabine and he authorised expenditure on large projects beyond the Society’s means. Lindley could only expostulate and was unsuccessful in moderating his actions, by 1830, the Society had mounting debts and a committee of enquiry was set up. Sabine resigned as Secretary and Lindley successfully defended his own position and carried the Society forward with the new Honorary Secretary, an eminent botanist of the time, John Claudius Loudon, sought Lindley’s collaboration on his “Encyclopedia of Plants”

31.
Arthur Cronquist
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Arthur John Cronquist was a United States biologist, botanist and a specialist on Compositae. He is considered one of the most influential botanists of the 20th century, two plant genera in the aster family have been named in his honor. These are Cronquistia, a synonym of Carphochaete, and Cronquistianthus. The former was applied by R. M, king and the latter by him and Harold E. Robinson. Arthur Cronquist was born on March 19,1919 in San Jose, California and his parents divorced when he was young and he and his older sister were brought up by his mother who worked for the Union Pacific Railroad in Pocatello. The young boy was an member of the Boy Scouts of America. He did his work at the Southern Branch of the University of Idaho. During his time there he studied botany under Ray J. Davis. After receiving his bachelors degree in 1938 in Biology, he went on to earn a degree in Biology at Utah State University in 1940 working under Bassett Maguire. In the same year he married Mabel Allred, who he remained with until his death and they had two children and a fondness for cats. Due to an accident, Cronquists right arm was partially disabled. Instead he began work on his doctorate at the University of Minnesota under C. O, rosendahl, earning his PhD in Botany in 1944. His dissertation was a revision of the genus Erigeron, from 1946 to 1948 he held a position at the University of Georgia, followed by a three-year position at Washington State University. Before returning to the New York Botanical Garden where he would spend the rest of his career, foreign Aid Program from 1951 to 1952. He died of heart failure on March 22,1992 while studying specimens of Mentzelia at the herbarium at Brigham Young University and his initial publication dealt purely with dicotyledons. Each of them would go on to produce their own taxonomic schemes, while working on the project in the 1960s, Cronquist came to be close friends with Armen Takhtajan and both men put all of their information at one anothers disposal. To this end Cronquist decided to learn Russian in order to have access to the literature that the Soviet Union had accumulated. He made several trips to the U. S. S. R. to meet with Takhtajan and other Soviet botanists and this work also was a survey of the practices of systematic botany

32.
Family (biology)
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In biological classification, family is one of the eight major taxonomic ranks, it is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks above the rank of genus. In vernacular usage, a family may be named one of its common members, for example, walnuts and hickory trees belong to the family Juglandaceae. What does or does not belong to a family—or whether a family should be recognized at all—are proposed and determined by practicing taxonomists. There are no rules for describing or recognizing a family. Taxonomists often take different positions about descriptions of taxa, and there may be no broad consensus across the community for some time. Some described taxa are accepted broadly and quickly, but others only rarely, if at all, the naming of families is codified by various international codes. In zoological nomenclature, the names of animals end with the suffix -idae. The concept of rank at time was not yet settled, and in the preface to the Prodromus Magnol spoke of uniting his families into larger genera. Carolus Linnaeus used the word familia in his Philosophia botanica to denote groups of plants, trees, herbs, ferns, palms. He used this term only in the section of the book. In zoology, the family as an intermediate between order and genus was introduced by Pierre André Latreille in his Précis des caractères génériques des insectes. He used families in some but not in all his orders of insects, families can be used for evolutionary, palaeontological and generic studies because they are more stable than lower taxonomic levels such as genera and species

33.
Genus
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A genus is a taxonomic rank used in the biological classification of living and fossil organisms in biology. In the hierarchy of classification, genus comes above species. In binomial nomenclature, the name forms the first part of the binomial species name for each species within the genus. Felis catus and Felis silvestris are two species within the genus Felis, Felis is a genus within the family Felidae. The composition of a genus is determined by a taxonomist, the standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. Moreover, genera should be composed of units of the same kind as other genera. The term comes from the Latin genus, a noun form cognate with gignere, linnaeus popularized its use in his 1753 Species Plantarum, but the French botanist Joseph Pitton de Tournefort is considered the founder of the modern concept of genera. The scientific name of a genus may be called the name or generic epithet. It plays a role in binomial nomenclature, the system of naming organisms. The rules for the names of organisms are laid down in the Nomenclature Codes. The standard way of scientifically describing species and other lower-ranked taxa is by binomial nomenclature, the generic name forms its first half. For example, the gray wolfs binomial name is Canis lupus, with Canis being the name shared by the wolfs close relatives. The specific name is written in lower-case and may be followed by names in zoology or a variety of infraspecific names in botany. Especially with these names, when the generic name is known from context. Because animals are typically only grouped within subspecies, it is written as a trinomen with a third name. Dog breeds, meanwhile, are not scientifically distinguished, there are several divisions of plant species and therefore their infraspecific names generally include contractions explaining the relation. For example, the genus Hibiscus includes hundreds of other species apart from the Rose of Sharon or common garden hibiscus, Rose of Sharon doesnt have subspecies but has cultivars that carry desired traits, such as the bright white H. syriaca Diana. Hawaiian hibiscus, meanwhile, includes several separate species, since not all botanists agree on the divisions or names between species, it is common to specify the source of the name using author abbreviations

34.
Species
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In biology, a species is the basic unit of biological classification and a taxonomic rank. A species is defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is problematic, for example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Other ways of defining species include similarity of DNA, morphology, all species are given a two-part name, a binomial. The first part of a binomial is the genus to which the species belongs, the second part is called the specific name or the specific epithet. For example, Boa constrictor is one of four species of the Boa genus, Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped that species could evolve given sufficient time, Charles Darwins 1859 book The Origin of Species explained how species could arise by natural selection. Genes can sometimes be exchanged between species by horizontal transfer, and species may become extinct for a variety of reasons. In his biology, Aristotle used the term γένος to mean a kind, such as a bird or fish, a kind was distinguished by its attributes, for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance, when observers in the Early Modern period began to develop systems of organization for living things, they placed each kind of animal or plant into a context. Many of these early delineation schemes would now be considered whimsical, animals likewise that differ specifically preserve their distinct species permanently, one species never springs from the seed of another nor vice versa. In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics and he established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships. At the time, however, it was widely believed that there was no organic connection between species, no matter how similar they appeared. However, whether or not it was supposed to be fixed, by the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time, in 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals and this required a new definition of species. Darwin concluded that species are what appear to be, ideas

35.
Gymnosperm
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The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes. The term gymnosperm comes from the Greek composite word γυμνόσπερμος, meaning naked seeds and their naked condition stands in contrast to the seeds and ovules of flowering plants, which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, often modified to form cones, the gymnosperms and angiosperms together compose the spermatophytes or seed plants. By far the largest group of living gymnosperms are the conifers, followed by cycads, gnetophytes, in early classification schemes, the gymnosperms were regarded as a natural group. There is conflicting evidence on the question of whether the living gymnosperms form a clade, for the most recent classification on extant gymnosperms see Christenhusz et al. There are 12 families,83 known genera with a total of ca 1080 known species, subclass Cycadidae Order Cycadales Family Cycadaceae, Cycas Family Zamiaceae, Dioon, Bowenia, Macrozamia, Lepidozamia, Encephalartos, Stangeria, Ceratozamia, Microcycas, Zamia. It is widely accepted that the gymnosperms originated in the late Carboniferous period and this appears to have been the result of a whole genome duplication event around 319 million years ago. Early characteristics of seed plants were evident in fossil progymnosperms of the late Devonian period around 383 million years ago, the scorpionflies likely engaged in pollination mutualisms with gymnosperms, long before the similar and independent coevolution of nectar-feeding insects on angiosperms. Evidence has also found that mid-Mesozoic gymnosperms were pollinated by Kalligrammatid lacewings. Conifers are by far the most abundant extant group of gymnosperms with six to eight families, with a total of 65-70 genera, conifers are woody plants and most are evergreens. The leaves of many conifers are long, thin and needle-like, other species, including most Cupressaceae and some Podocarpaceae, have flat, agathis in Araucariaceae and Nageia in Podocarpaceae have broad, flat strap-shaped leaves. Cycads are the next most abundant group of gymnosperms, with two or three families,11 genera, and approximately 338 species, the other extant groups are the 95-100 species of Gnetales and one species of Ginkgo. Pine, fir, spruce, and cedar are all examples of conifers that are used for lumber, some other common uses for gymnosperms are soap, varnish, nail polish, food, gum, and perfumes. Gymnosperms, like all plants, have a sporophyte-dominant life cycle. Two spore types, microspores and megaspores, are produced in pollen cones or ovulate cones. Gametophytes, as with all plants, develop within the spore wall. Pollen grains mature from microspores, and ultimately produce sperm cells, megagametophytes develop from megaspores and are retained within the ovule. During pollination, pollen grains are transferred between plants, from pollen cone to the ovule, being transferred by wind or insects

36.
Flower
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A flower, sometimes known as a bloom or blossom, is the reproductive structure found in plants that are floral. The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs, Flowers may facilitate outcrossing or allow selfing. Some flowers produce diaspores without fertilization, Flowers contain sporangia and are the site where gametophytes develop. Many flowers have evolved to be attractive to animals, so as to them to be vectors for the transfer of pollen. After fertilization, the ovary of the flower develops into fruit containing seeds, the essential parts of a flower can be considered in two parts, the vegetative part, consisting of petals and associated structures in the perianth, and the reproductive or sexual parts. A stereotypical flower consists of four kinds of structures attached to the tip of a short stalk, each of these kinds of parts is arranged in a whorl on the receptacle. The four main whorls are as follows, Collectively the calyx, corolla, the next whorl toward the apex, composed of units called petals, which are typically thin, soft and colored to attract animals that help the process of pollination. Androecium, the whorl, consisting of units called stamens. Stamens consist of two parts, a called a filament, topped by an anther where pollen is produced by meiosis. Gynoecium, the innermost whorl of a flower, consisting of one or more units called carpels, the carpel or multiple fused carpels form a hollow structure called an ovary, which produces ovules internally. Ovules are megasporangia and they in turn produce megaspores by meiosis which develop into female gametophytes and these give rise to egg cells. The gynoecium of a flower is described using an alternative terminology wherein the structure one sees in the innermost whorl is called a pistil. A pistil may consist of a carpel or a number of carpels fused together. The sticky tip of the pistil, the stigma, is the receptor of pollen, the supportive stalk, the style, becomes the pathway for pollen tubes to grow from pollen grains adhering to the stigma. The relationship to the gynoecium on the receptacle is described as hypogynous, perigynous, although the arrangement described above is considered typical, plant species show a wide variation in floral structure. These modifications have significance in the evolution of flowering plants and are used extensively by botanists to establish relationships among plant species, the four main parts of a flower are generally defined by their positions on the receptacle and not by their function. Many flowers lack some parts or parts may be modified into other functions and/or look like what is typically another part, in some families, like Ranunculaceae, the petals are greatly reduced and in many species the sepals are colorful and petal-like. Other flowers have modified stamens that are petal-like, the flowers of Peonies and Roses are mostly petaloid stamens

37.
Endosperm
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Endosperm is a tissue produced inside the seeds of most of the flowering plants following fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and this can make endosperm a source of nutrition in the human diet. For example, wheat endosperm is ground into flour for bread, other examples of endosperm that forms the bulk of the edible portion are coconut meat and coconut water, and corn. Some plants, such as orchids, lack endosperm in their seeds, in more derived flowering plants the embryo occupies most of the seed and the endosperm is non developed or consumed before the seed matures. Endosperm is formed when the two sperm nuclei inside a pollen grain reach the interior of a female gametophyte, one sperm nucleus fertilizes the egg cell, forming a zygote, while the other sperm nucleus usually fuses with the binucleate central cell, forming a primary endosperm cell. That cell created in the process of double fertilization develops into the endosperm, because it is formed by a separate fertilization, the endosperm constitutes an organism separate from the growing embryo. About 70% of angiosperm species have endosperm cells that are polyploid and these are typically triploid, but can vary widely from diploid to 15n. One species of flowering plant, Nuphar polysepala, has endosperm that is diploid, resulting from the fusion of a nucleus with one. There are three types of Endosperm development, Nuclear endosperm formation - where repeated free-nuclear divisions take place, commonly referred to as liquid endosperm. Coconut water is an example of this, cellular endosperm formation - where a cell-wall formation is coincident with nuclear divisions. Acoraceae has cellular endosperm development while other monocots are helobial, the evolutionary origins of double fertilization and endosperm are unclear, attracting researcher attention for over a century. There are the two hypotheses, The double fertilization initially used to produce two identical, independent embryos. Later these embryos acquired different roles, one growing into the mature organism, thus the early endosperm was probably diploid, like the embryo. Some gymnosperms, such as Ephedra, may produce twin embryos by double fertilization, either of these two embryos is capable of filling in the seed, but normally only one develops further. Also, most basal angiosperms still contain the embryo sac. Endosperm is the remnant of the actual gametophyte, similar to the complex multicellular gametophytes found in gymnosperms. In this case, acquisition of the nucleus from the sperm cell is a later evolutionary step. This nucleus may provide the organism with some control over endosperm development

38.
Seed
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A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction in seed plants, Seeds are the product of the ripened ovule, after fertilization by pollen and some growth within the mother plant. The embryo is developed from the zygote and the coat from the integuments of the ovule. Seed plants now dominate biological niches on land, from forests to both in hot and cold climates. The term seed also has a meaning that antedates the above—anything that can be sown, e. g. seed potatoes. In the case of sunflower and corn seeds, what is sown is the seed enclosed in a shell or husk, many structures commonly referred to as seeds are actually dry fruits. Plants producing berries are called baccate, sunflower seeds are sometimes sold commercially while still enclosed within the hard wall of the fruit, which must be split open to reach the seed. Different groups of plants have other modifications, the stone fruits have a hardened fruit layer fused to. Nuts are the one-seeded, hard-shelled fruit of plants with an indehiscent seed. Seeds are produced in several related groups of plants, and their manner of production distinguishes the angiosperms from the gymnosperms, angiosperm seeds are produced in a hard or fleshy structure called a fruit that encloses the seeds, hence the name. Some fruits have layers of hard and fleshy material. In gymnosperms, no special structure develops to enclose the seeds, however, the seeds do become covered by the cone scales as they develop in some species of conifer. Seed production in natural plant populations varies widely from year-to-year in response to weather variables, insects and diseases, over a 20-year period, for example, forests composed of loblolly pine and shortleaf pine produced from 0 to nearly 5 million sound pine seeds per hectare. Over this period, there were six bumper, five poor, and nine good seed crops, right after fertilization, the zygote is mostly inactive, but the primary endosperm divides rapidly to form the endosperm tissue. This tissue becomes the food the young plant will consume until the roots have developed after germination, after fertilization the ovules develop into the seeds. The ovule consists of a number of components, The funicle or seed stalk which attaches the ovule to the placenta and hence ovary or fruit wall, the nucellus, the remnant of the megasporangium and main region of the ovule where the megagametophyte develops. The micropyle, a pore or opening in the apex of the integument of the ovule where the pollen tube usually enters during the process of fertilization. The chalaza, the base of the ovule opposite the micropyle, the shape of the ovules as they develop often affects the final shape of the seeds

39.
Fruit
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In botany, a fruit is the seed-bearing structure in flowering plants formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate seeds, accordingly, fruits account for a substantial fraction of the worlds agricultural output, and some have acquired extensive cultural and symbolic meanings. On the other hand, in usage, fruit includes many structures that are not commonly called fruits, such as bean pods, corn kernels, tomatoes. The section of a fungus that produces spores is called a fruiting body. Many common terms for seeds and fruit do not correspond to the botanical classifications, however, in botany, a fruit is the ripened ovary or carpel that contains seeds, a nut is a type of fruit and not a seed, and a seed is a ripened ovule. Examples of culinary vegetables and nuts that are botanically fruit include corn, cucurbits, eggplant, legumes, sweet pepper, in addition, some spices, such as allspice and chili pepper, are fruits, botanically speaking. g. Botanically, a grain, such as corn, rice, or wheat, is also a kind of fruit. However, the wall is very thin and is fused to the seed coat. The outer, often edible layer, is the pericarp, formed from the ovary and surrounding the seeds, the pericarp may be described in three layers from outer to inner, the epicarp, mesocarp and endocarp. Fruit that bears a prominent pointed terminal projection is said to be beaked, a fruit results from maturation of one or more flowers, and the gynoecium of the flower forms all or part of the fruit. Inside the ovary/ovaries are one or more ovules where the megagametophyte contains the egg cell, after double fertilization, these ovules will become seeds. The ovules are fertilized in a process starts with pollination. After pollination, a tube grows from the pollen through the stigma into the ovary to the ovule, later the zygote will give rise to the embryo of the seed, and the endosperm mother cell will give rise to endosperm, a nutritive tissue used by the embryo. As the ovules develop into seeds, the ovary begins to ripen and the ovary wall, in some multiseeded fruits, the extent to which the flesh develops is proportional to the number of fertilized ovules. The pericarp is often differentiated into two or three distinct layers called the exocarp, mesocarp, and endocarp, in some fruits, especially simple fruits derived from an inferior ovary, other parts of the flower, fuse with the ovary and ripen with it. In other cases, the sepals, petals and/or stamens and style of the fall off. When such other floral parts are a significant part of the fruit, it is called an accessory fruit, since other parts of the flower may contribute to the structure of the fruit, it is important to study flower structure to understand how a particular fruit forms. There are three modes of fruit development, Apocarpous fruits develop from a single flower having one or more separate carpels

40.
Greek language
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Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population

41.
Pinophyta
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The Pinophyta, also known as Coniferophyta or Coniferae, or commonly as conifers, are a division of vascular land plants containing a single class, Pinopsida. They are gymnosperms, cone-bearing seed plants, all extant conifers are perennial woody plants with secondary growth. The great majority are trees, though a few are shrubs, examples include cedars, Douglas firs, cypresses, firs, junipers, kauri, larches, pines, hemlocks, redwoods, spruces, and yews. As of 1998, the division Pinophyta was estimated to contain eight families,68 genera, although the total number of species is relatively small, conifers are ecologically important. They are the dominant plants over large areas of land, most notably the taiga of the Northern Hemisphere, boreal conifers have many wintertime adaptations. The narrow conical shape of northern conifers, and their downward-drooping limbs, many of them seasonally alter their biochemistry to make them more resistant to freezing. While tropical rainforests have more biodiversity and turnover, the conifer forests of the world represent the largest terrestrial carbon sink. Conifers are of economic value for softwood lumber and paper production. The earliest conifers in the record date to the late Carboniferous period, possibly arising from Cordaites. Pinophytes, Cycadophytes, and Ginkgophytes all developed at this time, an important adaptation of these gymnosperms was allowing plants to live without being so dependent on water. Other adaptations are pollen and the seed, which allows the embryo to be transported and developed elsewhere, Conifers appear to be one of the taxa that benefited from the Permian–Triassic extinction event, and were the dominant land plants of the Mesozoic. They were overtaken by the plants, which first appeared in the Cretaceous. They were the food of herbivorous dinosaurs, and their resins and poisons would have given protection against herbivores. Reproductive features of modern conifers had evolved by the end of the Mesozoic era, Conifer is a Latin word, a compound of conus and ferre, meaning the one that bears cone. A descriptive name in use for the conifers is Coniferae. Alternatively, descriptive botanical names may also be used at any rank above family and this means that if conifers are considered a division, they may be called Pinophyta or Coniferae. As a class they may be called Pinopsida or Coniferae, as an order they may be called Pinales or Coniferae or Coniferales. Conifers are the largest and economically most important component group of the gymnosperms, the division Pinophyta consists of just one class, Pinopsida, which includes both living and fossil taxa

42.
Reproductive organ
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The external and visible organs, in males and females, are the primary sex organs known as the genitals or genitalia. The internal organs are known as the sex organs and are sometimes referred to as the internal genitalia. The characteristics that begin to appear during puberty, such as, in humans, mosses, ferns, and some similar plants have gametangia for reproductive organs, which are part of the gametophyte. The flowers of flowering plants produce pollen and egg cells, but the sex organs themselves are inside the gametophytes within the pollen, coniferous plants likewise produce their sexually reproductive structures within the gametophytes contained within the cones and pollen. The cones and pollen are not themselves sexual organs, the other, hidden sex organs are referred to as the secondary sex organs or internal genitalia. The most important of these are the gonads, a pair of sex organs, gonads are the true sex organs, generating reproductive gametes containing inheritable DNA. They also produce most of the hormones that affect sexual development. The visible portion of the genitals for males consists of the scrotum and penis, for females, it consists of the vulva. In placental mammals, females have two genital orifices, the vagina and urethra, while males have one, the urethra. Male and female genitals have many nerve endings, resulting in pleasurable, in most human societies, particularly in conservative ones, exposure of the genitals is considered a public indecency. In mammals, sex organs include, In typical prenatal development, sexual organs originate from a common anlage anatomy during early gestation, the SRY gene, usually located on the Y chromosome and encoding the testis determining factor, determines the direction of this differentiation. The absence of it allows the gonads to continue to develop into ovaries, thereafter, the development of the internal reproductive organs and the external genitalia is determined by hormones produced by certain fetal gonads and the cells response to them. The initial appearance of the fetal genitalia looks basically feminine, a pair of urogenital folds with a protuberance in the middle. Each sexual organ in one sex has a counterpart in the other one. See a list of homologues of the reproductive system. Furthermore, differences in brain structure arise, affecting, but not absolutely determining, intersex is the development of genitalia somewhere between typical male and female genitalia. Some parents allow their doctors to choose, if they do decide to modify the genitalia, they have approximately a 50% chance of getting genitalia that will match the childs gender identity. If they pick the one, their child may begin to show symptoms of transsexualism

43.
Ecological niche
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In ecology, a niche is a term with a variety of meanings related to the behavior of a species living under specific environmental conditions. The ecological niche describes how an organism or population responds to the distribution of resources and competitors, the notion of ecological niche is central to ecological biogeography, which focuses on spatial patterns of ecological communities. Species distributions and their dynamics over time result from properties of the species, and interactions between the two — in particular the abilities of some species, especially our own, to modify their environments and alter the range dynamics of many other species. Alteration of a niche by its inhabitants is the topic of niche construction. Island biogeography can help explain island species and associated unfilled niches, the ecological meaning of niche comes from the meaning of niche as a recess in a wall for a statue, which itself is probably derived from the Middle French word nicher, meaning to nest. The Grinnellian niche concept embodies the idea that the niche of a species is determined by the habitat in which it lives, in other words, the niche is the sum of the habitat requirements and behaviors that allow a species to persist and produce offspring. Its niche is defined by the felicitous complementing of the thrashers behavior and this perspective of niche allows for the existence of both ecological equivalents and empty niches. In 1927 Charles Sutherland Elton, a British ecologist, defined a niche as follows, The niche of an animal means its place in the environment, its relations to food. Elton classified niches according to foraging activities, For instance there is the niche that is filled by birds of prey which eat small animals such as shrews, in an oak wood this niche is filled by tawny owls, while in the open grassland it is occupied by kestrels. Conceptually, the Eltonian niche introduces the idea of a response to. In an extreme example, beavers require certain resources in order to survive and reproduce, thus, the beaver affects the biotic and abiotic conditions of other species that live in and near the watershed. In a more subtle case, competitors that consume resources at different rates can lead to cycles in resource density that differ between species, not only do species grow differently with respect to resource density, their own population growth can lead to different effects on resource density over time. The hypervolume defines the space of resources available to organisms. The niche concept was popularized by the zoologist G. Evelyn Hutchinson in 1957, Hutchinson inquired into the question of why there are so many types of organisms in any one habitat. For such a distribution, the position, width and form of the niche correspond to the mean, standard deviation. This postulate, however, can be misguided, as it ignores the impacts that the resources of each category have on the organism, for instance, the resource in the overlap region can be non-limiting, in which case there is no competition for this resource despite niche overlap. An organism free of interference from other species could use the range of conditions and resources in which it could survive. Hutchinson used the idea of competition for resources as the mechanism driving ecology

44.
Terrestrial ecoregion
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An ecoregion is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than an ecozone. All three of these are less or greater than an ecosystem. Ecoregions cover relatively large areas of land or water, and contain characteristic, the biodiversity of flora, fauna and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions. Three caveats are appropriate for all bio-geographic mapping approaches, firstly, no single bio-geographic framework is optimal for all taxa. Ecoregions reflect the best compromise for as many taxa as possible, secondly, ecoregion boundaries rarely form abrupt edges, rather, ecotones and mosaic habitats bound them. Thirdly, most ecoregions contain habitats that differ from their assigned biome, biogeographic provinces may originate due to various barriers. Some physical, some climatic and some ocean chemical related, the history of the term is somewhat vague as it was used in many contexts, forest classifications, biome classifications, biogeographic classifications, etc. The concept of ecoregion of Bailey gives more importance to ecological criteria, while the WWF concept gives more importance to biogeography, there is significant, but not absolute, spatial correlation among these characteristics, making the delineation of ecoregions an imperfect science. Such transition zones are called ecotones, Ecoregions can be categorized using an algorithmic approach or a holistic, “weight-of-evidence” approach where the importance of various factors may vary. An example of the approach is Robert Bailey’s work for the U. S. The intended purpose of ecoregion delineation may affect the method used, according to WWF, the boundaries of an ecoregion approximate the original extent of the natural communities prior to any major recent disruptions or changes. WWF has identified 867 terrestrial ecoregions, and approximately 450 freshwater ecoregions across the Earth, the use of the term ecoregion is an outgrowth of a surge of interest in ecosystems and their functioning. In particular, there is awareness of issues relating to spatial scale in the study and it is widely recognized that interlinked ecosystems combine to form a whole that is greater than the sum of its parts. The Global 200 is the list of ecoregions identified by WWF as priorities for conservation, Terrestrial ecoregions are land ecoregions, as distinct from freshwater and marine ecoregions. In this context, terrestrial is used to mean of land, WWF ecologists currently divide the land surface of the Earth into 8 major ecozones containing 867 smaller terrestrial ecoregions. The WWF effort is a synthesis of previous efforts to define. Many consider this classification to be decisive, and some propose these as stable borders for bioregional democracy initiatives. The eight terrestrial ecozones follow the major floral and faunal boundaries, identified by botanists and zoologists, ecozone boundaries generally follow continental boundaries, or major barriers to plant and animal distribution, like the Himalayas and the Sahara

45.
Stamen
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The stamen is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium, a stamen typically consists of a stalk called the filament and an anther which contains microsporangia. Most commonly anthers are two-lobed and are attached to the filament either at the base or in the area of the anther. The sterile tissue between the lobes is called the connective, a pollen grain develops from a microspore in the microsporangium and contains the male gametophyte. The stamens in a flower are called the androecium. The androecium can consist of as few a one-half stamen as in Canna species or as many as 3,482 stamens which have been counted in Carnegiea gigantea, the androecium in various species of plants forms a great variety of patterns, some of them highly complex. It surrounds the gynoecium and is surrounded by the perianth, a few members of the family Triuridaceae, particularly Lacandonia schismatica, are exceptional in that their gynoecia surround their androecia. Stamen is the Latin word meaning thread, depending on the species of plant, some or all of the stamens in a flower may be attached to the petals or to the floral axis. They also may be free-standing or fused to one another in different ways, including fusion of some. The filaments may be fused and the free, or the filaments free. Rather than there being two locules, one locule of a stamen may fail to develop, or alternatively the two locules may merge late in development to give a single locule, a typical anther contains four microsporangia. The microsporangia form sacs or pockets in the anther, the two separate locules on each side of an anther may fuse into a single locule. Each microsporangium is lined with a tissue layer called the tapetum. These undergo meiosis to form haploid spores, the spores may remain attached to each other in a tetrad or separate after meiosis. Each microspore then divides mitotically to form an immature microgametophyte called a pollen grain, the pollen is eventually released when the anther forms openings. These may consist of longitudinal slits, pores, as in the family, or by valves. More commonly, mature pollen grains separate and are dispensed by wind or water, pollinating insects, pollen of angiosperms must be transported to the stigma, the receptive surface of the carpel, of a compatible flower, for successful pollination to occur. After arriving, the pollen grain typically completes its development and it may grow a pollen tube and undergoing mitosis to produce two sperm nuclei

The Ordovician () is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician …

External mold of Ordovician bivalve showing that the original aragonite shell dissolved on the sea floor, leaving a cemented mold for biological encrustation (Waynesville Formation of Franklin County, Indiana).

A fluorescent image of an endothelial cell. Nuclei are stained blue, mitochondria are stained red, and microfilaments are stained green.

Human cancer cells with nuclei (specifically the DNA) stained blue. The central and rightmost cell are in interphase, so the entire nuclei are labeled. The cell on the left is going through mitosis and its DNA has condensed.

Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – …

Production of new individuals along a leaf margin of the miracle leaf plant (Kalanchoe pinnata). The small plant in front is about 1 cm (0.4 in) tall. The concept of "individual" is obviously stretched by this asexual reproductive process.

Image: Mitosis

Image: Meiosis

Illustration of the twofold cost of sexual reproduction. If each organism were to contribute to the same number of offspring (two), (a) the population remains the same size each generation, where the (b) asexual population doubles in size each generation.